This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. It is now clear that intestine and other mucosal tissues are of major importance in both the transmission as well as the early pathogenesis of HIV infection. Last year we demonstrated that HIV-specific IgA and IgG are preferentially secreted from the intestine (rectum) and vagina, respectively following intravenous administration. We are now determining whether systemic or intravaginal administration of IgA or IgG may be better at protection against a vaginal SHIV challenge. For example, if we find that anti-HIV antibodies when in an IgA isotype are more protective than IgG isotypes, this could be highly relevant for HIV vaccine design.